Evaluating the Tamm–Dancoff Approximation for Two-Photon Absorption Properties
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Bibliographic record
Abstract
Two-photon absorption (2PA) is a powerful tool in nonlinear optics, enabling advanced applications like high-resolution microscopy and photodynamic therapy. In this study, we explore the 2PA properties of 20 chromophores using time-dependent density-functional theory (TD-DFT), TD-DFT with the Tamm–Dancoff approximation (TDA), and the resolution-of-identity approximation in conjunction with the second-order approximate coupled-cluster (RI-CC2). TDA’s performance in predicting 2PA properties remains insufficiently characterized compared to (full) TD-DFT, where the functionals CAM-B3LYP, MN15, and ωB97X are used, and their results are compared to RI-CC2. This comparison involves assessing key photophysical properties, including 2PA cross sections (σ 2PA ) and dipole moments (μ 00, μ 11, μ 01, and Δμ). Among the tested functionals, MN15 demonstrated the lowest mean absolute errors (MAEs) for the computed photophysical properties for both TDA and TD-DFT. Our findings indicate that TDA captures qualitative trends and provides slightly more accurate quantitative predictions with generally lower MAEs than TD-DFT. These findings suggest that the use of TDA has significant potential as a cost-effective alternative to (full) TD-DFT for predicting 2PA properties.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it